In the previously issued patent of the present inventor, a sample collection system was disclosed. Briefly, it utilizes a reciprocating plunger which moves a solid member against a resilient plug having a dished area. When immersed in fluid, the dished area captures fluid. As pressure is applied, the dished area is reduced in volume and thereby forces the captured fluid to flow through a check valve in the solid member. The check valve connects with a flow line, and the sample is removed by this procedure. Sampling rate is controlled rather easily, and the sample is delivered in a predictable fashion. The sample is captured in measured quantity and flows through the check valve.
A sample collection probe apparatus of this nature functions in a cyclical fashion, perhaps operating several times per minute. Typically, they are operated around the clock. This inevitably places substantial wear on the resilient plug. Because it is compressed and flexed repetitively, it runs the risk of fatigue and tearing. This particularly is aggravated because there is fatigue as it is pressured to closure, and there is also fatigue as the components are pulled apart, thereby breaking the vacuum formed in the dished area. Assume for descriptive purposes that the dished area is reduced in volume by 99%. The fluid captured in that area is forced out through a check valve. As the parts are pulled back from one another, the dished area expands and pulls a vacuum. This vacuum tends to distort the lip area encircling the dished plug, and damage may occur. The resilient plug has been held successfully in place by means of an overlayed peripheral lip locking against the body of the resilient plug and lapping over the exposed face. While this has met with some success, there is still a tendency for fractures to be formed in the resilient plug. Such fractures damage the plug, and initiate delamination, that is, the breaking away of substantial portions of the resilient plug.
The present apparatus is an improvement which extends the life of the resilient plug by breaking the vacuum which is formed at the time the parts are retracted from one another. The component parts are forced together and the resilient plug is deformed. Thereafter, they are pulled apart and vacuum is formed as described above. With this apparatus, the vacuum does not persist for very long, and the vacuum is relieved by moving a cannister type cap over the end of the solid member. This is typically on the end of the probe. This cannister or cap telescopes, and forms a seal when jammed against the resilient plug in the intended fashion. Telescoping movement permits it to separate slightly, thereby creating a leakage path which breaks the vacuum. This leakage path relieves vacuum in the area of the dished recess and enables the two parts to be separated.